O clima influência diretamente a dinâmica da fauna do Eoceno na América do Norte

Climate directly influences Eocene mammal faunal dynamics in North America

Michael O. Woodburnea,1, Gregg F. Gunnellb and Richard K. Stuckyc

+Author Affiliations

aDepartment of Geology, Museum of Northern Arizona, Flagstaff, AZ 86001;

bMuseum of Paleontology, University of Michigan, Ann Arbor, MI 48109; and

cDenver Museum of Nature and Science, Denver, CO 80205

Communicated by W. A. Berggren, Woods Hole Oceanographic Institution, Woods Hole, MA, June 19, 2009 (received for review December 18, 2008)

Abstract

The modern effect of climate on plants and animals is well documented. Some have cautioned against assigning climate a direct role in Cenozoic land mammal faunal changes. We illustrate 3 episodes of significant mammalian reorganization in the Eocene of North America that are considered direct responses to dramatic climatic events. The first episode occurred during the Paleocene–Eocene Thermal Maximum (PETM), beginning the Eocene (55.8 Ma), and earliest Wasatchian North American Land Mammal Age (NALMA). The PETM documents a short (<170 k.y.) global temperature increase of ≈5 °C and a substantial increase in first appearances of mammals traced to climate-induced immigration. A 4-m.y. period of climatic and evolutionary stasis then ensued. The second climate episode, the late early Eocene Climatic Optimum (EECO, 53–50 Ma), is marked by a temperature increase to the highest prolonged Cenozoic ocean temperature and a similarly distinctive continental interior mean annual temperature (MAT) of 23 °C. This MAT increase [and of mean annual precipitation (MAP) to 150 cm/y) promoted a major increase in floral diversity and habitat complexity under temporally unique, moist, paratropical conditions. Subsequent climatic deterioration in a third interval, from 50 to 47 Ma, resulted in major faunal diversity loss at both continental and local scales. In this Bridgerian Crash, relative abundance shifted from very diverse, evenly represented, communities to those dominated by the condylarth Hyopsodus. Rather than being “optimum,” the EECO began the greatest episode of faunal turnover of the first 15 m.y. of the Cenozoic.

Bridgerian Crash climate change EECO faunal change mammal faunas

Footnotes

1To whom correspondence should be addressed. E-mail: mikew@npgcable.com

Author contributions: M.O.W. designed research; M.O.W., G.F.G., and R.K.S. performed research; M.O.W., G.F.G., and R.K.S. analyzed data; and M.O.W. wrote the paper.

The authors declare no conflict of interest.

This article contains supporting information online at www.pnas.org/cgi/content/full/0906802106/DCSupplemental.

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